The geotechnical scope included the design and detailing of ground improvement schemes, track bed treatment, retaining walls and cut slope stabilisation along the alignment and foundation for a number of viaducts and overhead caternary line (OCL) pole foundations for the high-speed rail connecting Kuala Lumpur Sentral to KLIA.
The civil engineering scope included the development of plan and profile drawings using centreline alignment and mainline drainage that includes culverts. The scope also covered all civil infrastructure works at the depot and stations as well as the respective access roads.
The 56-kilometre high speed (160 –180 km/hr) railway line connecting Kuala Lumpur Sentral station and Kuala Lumpur International Airport (KLIA) was completed in 2002. The railway line was introduced to create a fast and seamless connectivity between the airport and the city centre.
Since its commencement, KLIA Express, one of the two services on the Express Rail Link system, provides a non-stop express service that sees an annual ridership of over 1.6 million. The line is also part of the Klang Valley Integrated Transit System.
GCU has planned and supervised all the geotechnical investigations along the entire alignment. The first 17km of the alignment is on brown field with flat topography. It runs parallel to the existing KTM electrified double track line.
The majority of the first 17km alignment is on ex-tin mine tailings including a pond underlain by karstic limestone formation. The rest of the alignment is on greenfield with residual weathered formation with the presence of two flood plains at Sg Langat and Sg Labu. Sg Langat flood plain comprised ex-tin mine tailings of about 12m thick with a large pond while the Sg Labu floodplain comprised marine clay deposit of about 20m thick.
GCU designed and detailed a number of the ground improvement works for embankment on weak/soft ground. This includes geotextile reinforcement, partial replacements with surcharge preload, prefabricated vertical drains (PVD) with surcharge preload, stone column at high embankment, stabilisation against pond edge and sinkhole prone areas, complete reclamation of a mining pond and piled embankment.
At embankment areas that has weak subsoil and are prone to ground subsidence due to sinkhole formation, GCU adopted stone columns to treat and improve the foundation soil to a depth of 12m. In addition, drainage systems and impermeable soil covers were implemented to minimise the infiltration of surface water which are the likely trigger factors to the formation of sinkholes.
At the Sg Langat flood plain, the existing mining pond was reclaimed using complete removal of soft soil at the base and backfilled in layers using compacted suitable fill with the provision of balancing culverts. PVD with surcharge preload was adopted to treat the subsoil at the bridge approaches of this flood plain.
Over at the Sg Labu flood plain, piled embankment and complete replacement were adopted at the bridge approaches. A viaduct was built across the flood plain.
For the first 17km of the railway line underlain by weak soils up to 20m and constructed with low or nominal embankment, the track bed below the sub ballast was formed using 2m to 3m replacement with competent soil and reinforced with/without geotextile. This was designed using the British Threshold Stress Method to reduce the permanent cumulative plastic deformation of the track bed under the train repetitive loads.
Reinforced concrete (RC) retaining walls were mainly constructed at restricted areas to contain the railway embankment. Pipe and box culverts were used for cross drainage along the entire alignment depending on the location and volume of discharge.
Track drainage in the form of berm drains, toe drains, interceptor drains, and cascading drains were also provided. Baffle chutes were designed to reduce the water speed at certain locations to minimise the formation of hydraulic jumps.
OCL pole foundations in the form of RC driven piles, short bored piles and tube piles were constructed along the alignment. For viaducts, generally bored piles were adopted as the foundation piles. In some places, single large diameter bored piles were designed and constructed.
Soil nails using grid beam system and shotcrete were adopted to stabilise the steep slope at one location. At another location that is close to existing high-rise apartments, contiguous bored pile with reinforced soil wall founded on discrete pile caps with individual piles were constructed top of the CBP wall. The normal cut slopes gradient at greenfield were designed based on geological, subsoil conditions and groundwater profile with varying gradients.
GCU worked closely with SPYTL and other contractors during the design and construction phases. To provide further design and technical support, GCU stationed a team of engineers at the project office to manage and coordinate the design changes during construction.
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